Cooling turbos down ?

[blade7]

Krikkit said:

I imagine the newer cars with electric water pumps will keep circulating after the engine is off if the turbo is too hot anyway.

944 turbo's have an electric pump that circulates water through the turbo after shut down.

[mrmr96]

blade7 said:

Krikkit said:

I imagine the newer cars with electric water pumps will keep circulating after the engine is off if the turbo is too hot anyway.

944 turbo's have an electric pump that circulates water through the turbo after shut down.

And how will that prevent the oil coking? You need to keep the oil moving until it's cool. Not water.

[Mr2Mike]

mrmr96 said:

And how will that prevent the oil coking? You need to keep the oil moving until it's cool. Not water.

Because it stops the massive temperature rise in the bearings after the oil flow has stopped.

[RS4Audi]

Krikkit said:

I imagine the newer cars with electric water pumps will keep circulating after the engine is off if the turbo is too hot anyway.

Some older ones too, I know my Audi S2 from 1993 had an after-run pump and the S/RS4 has them too.
It even circulates the coolant in the opposite direction to when the engine is running to stop an air lock forming.
A lot of people change the sensor for when it kicks in so it comes on at a lower coolant temp.
Mine has got one and you can just hear the pump running after turning off the engine.
An upgraded oil cooler helps too. If I've been on a hard run and the oil temp is up from normal, a cruise home for the last few miles soon as it dropped down again

You can see it behind the centre grill

[GroundEffect]

Water cooling in turbo chargers is generally for cooling the housings, not the bearings. The oil cooling is still necessary for this function.

I only work on the coolant side of things so someone who designs turbos will be better equipped to comment but we use after-run pumps to cool turbo housings. Not sure if a similar function exists on the oil side.

[jshell]

Krikkit said:

I imagine the newer cars with electric water pumps will keep circulating after the engine is off if the turbo is too hot anyway.

Since at least 1989 and likely before Audi introduced post-shutdown water circulation for turbos.

[8bit]

V8 Disco said:

TheHeretic said:

You can buy turbo timers which keep the engine running for a predetermined time after you remove the keys from the ignition.

http://en.wikipedia.org/wiki/Turbo_timer

I have one on the Skyline; but can't bring myself to walk away from a locked, running car so don't use it.

I just cruise gently for the last few mins to let the turbo cool a bit.

It's illegal to leave a car unattended with the engine running, even off the public roads (e.g. driveway) so technically you'd be committing an offence by walking away while the turbo timer is still running.

[Fubar1977]

I don`t think it`s as important as it used to be but there`s certainly no harm in doing it.
I usually let mine idle for at least 30 secs before switching off, preceded by slower driving usually.

If I`m coming off a high speed motorway run into the services for example I`ll let it idle for at least a minute to let everything settle down.

Probably overcautious but can`t do any harm.

[mrmr96]

8bit said:

It's illegal to leave a car unattended with the engine running, even off the public roads (e.g. driveway) so technically you'd be committing an offence by walking away while the turbo timer is still running.

How do the police do it then?

[blade7]

jshell said:

Since at least 1989 and likely before Audi introduced post-shutdown water circulation for turbos.

1985 944T had the same I believe. It's not unusual for those turbo's to last 150k.

[ShaunTheSheep]

The VAG EA888 2.0 TSi as fitted across the various A3, A4, A5, Golf GTI, Passat, Octavia Vrs etc. continues to pump oil through the IHI turbo after ignition off.

These engines use the VW507.00 oil which is AFAIK one of the strictest specifications regarding resistance to breakdown at high temperatures, but the oil is still pumped after ignition off suggesting 1050 degree C (max operating temp for the IhI turbo) is too hot for any oil technology just now.

Source: being too much of a geek, can't help it, http://files.engineering.com/download.aspx?folder=...

[ShaunTheSheep]

mrmr96 said:

How do the police do it then?

http://www.legislation.gov.uk/uksi/1986/1078/regulation/107/made

[quote]
(2) The requirement specified in paragraph (1) as to the stopping of the engine shall not apply in respect of a vehicle—

(a) being used for ambulance, fire brigade or police purposes; or
...

Although AFAIK as soon as you press any pedal while run lock is engaged, the engine shuts off?

[cossy400]

My Cosworth had turbo timer fitted, and even after gentle miles off boost as such I would leave it running on the timer for a minute a so.

With regards to it being an offence, steering lock was on and doors locked.

Not like these dummies that leave it running on the drive defrosting unlocked.

But I did have a few people in the supermarket car park look at me funny as your walking away with it still running.

[RS4Audi]

There is no need for turbo timers, thats just from watching too much Fast & Furious!
As already mentioned, just drive off boost for the last few miles, which you are usually forced to do anyway unless you live on the side of a motorway or in the middle of nowhere.

I don't see the point of turbo timers anyway. What happens when your engine sits there idling?
All its doing it increasing engine temp, not lowering it.

[Gwagon111]

It's more a case of spool down, than cool down. You don't want to starve a fast spinning fluid bearing turbo of oil, whilst its still spinning at a rate of knots. Turbo timers, and oil temperature gauges, are fantastic things.

[RobGT81]

GroundEffect said:

Water cooling in turbo chargers is generally for cooling the housings, not the bearings. The oil cooling is still necessary for this function.

I only work on the coolant side of things so someone who designs turbos will be better equipped to comment but we use after-run pumps to cool turbo housings. Not sure if a similar function exists on the oil side.

Pumping the oil around the core doesn't really shift that much temperature to be honest. Best bet, as mentioned, is to just run off boost for the last few minutes of your drive to prevent heat soak from the turbine housing.

RS4Audi said:

I don't see the point of turbo timers anyway. What happens when your engine sits there idling?
All its doing it increasing engine temp, not lowering it.

At idle, your EGT is lower than it is when the engine is under load.

Edited by RobGT81 on Monday 6th May 13:28

[Monty Python]

http://www.gcg.com.au/index.php?option=com_content...

[McWigglebum4th]

8bit said:

It's illegal to leave a car unattended with the engine running, even off the public roads (e.g. driveway) so technically you'd be committing an offence by walking away while the turbo timer is still running.

Well i'm pubic enemy number 1

I'm always leaving my landrover running while it is boosting up something like my lawnmower before i start it up

[Johnnytheboy]

I've often wondered if engines with stop-start systems take this need to cool the turbo into account.

[Chuck328]

cossy400 said:

My Cosworth had turbo timer fitted, and even after gentle miles off boost as such I would leave it running on the timer for a minute a so.

With regards to it being an offence, steering lock was on and doors locked.

Not like these dummies that leave it running on the drive defrosting unlocked.

But I did have a few people in the supermarket car park look at me funny as your walking away with it still running.

Ditto.

However, as driving home is through the 'burbs', that is generally enough to let the turbo cool.

I also feel a tad guilty leaving the Evo running at idle when the neighbours are at home.